Question

a muscle fibre twitch is abrupt or all or none. a muscle contraction is smooth and graded. explain why

Answer 1

Twitch

• A muscle twitch is a contraction of muscel in respone to stimulus.
• This is an isolated contraction that can last for few milliseconds.
• The contraction occurs when the stimulus crosses the threshold.
• Hence it is called all- or none phenomenon. If stimulus is stronge enough to cross threshold there is action potential otherwise, no.
• But this single twitch does not produce significant muscle activity.

Muslce contraction

• A muscle contraction is smooth and graded.
• Here, a series of action potential to fibre is necessary to produce sustained muscle contraction.
• Once action potential is produced, it sustains over a longer period and travels larger distances.
• The contraction can be modified by input from nervous stem to prpduce varying amount of force - this is called graded muscle response.
• Smooth response is achived by summation of responses to successive stimuli and recruitment of motor units.